Title : Home Assignment II Faculty : BEL III/I
Unit Topic Hours Marks Remarks
2 Parallel Interfacing with Microprocessor Based System 4 8
Instructions:
− Date of issue : 2081 Jestha 22
− Read the following instructions/guidelines carefully before starting the assignment.
− Complete all the tasks and questions provided.
− Submit your completed assignment by 2081 Ashad 1, Saturday.
− Late submissions may incur a penalty unless prior arrangements have been made.
Submission Guidelines:
− Answers are to be presented in handwritten format.
− Ensure that your answers are organized clearly and labeled appropriately.
− Include your Name and Roll No. on each page of your submission.
− Submit your assignment in PDF via your Class Representative.
Grading Criteria:
− Your assignment will be graded based on submission,originality and completeness.
REVIEW QUESTIONS
1) A microprocessor kit has an onboard 8255.
a) Interface to the 8255 eight single-pole-double throw (SPDT) switches numberd S0 to S7
and a seven segment common anode LED display.
b) Draw the complete circuit setup.
c) Define clearly the functions of all ports.
d) Write a program to initialize 8255. Detect a switch closure and display the value of the
switch number on the LED display.
2) Design an interfacing circuit to set up bidirectional data communication in the master-
slave format between two 8085A microcomputers. Use the 8255A as the interface between
the master and the slave microcomputers.
a) What will be the port addresses and control word.
b) Write necessary program to transfer a block of data from the master to the slave along
with its flowchart diagram.
3) Draw the circuit diagram to interface 8255A PPI with 8085 microprocessor at base address
B0H. Write an assembly program that determines the addition of contents of port A and port
B and display the result in port C. Use appropriate control word to initialize the 8255A.
4) Port A is to be designed as the input for a keyboard in interrupt driven I/O and Port B as the
output for a printer in status check I/O using mode 1 of 8255 with 8085 microprocessor as
shown below:
a) Find port addresses by analyzing decoding logic.
b) Determine the control word to set up port A as input and port B as output.
c) Determine the BSR word to enable INTEA.
d) Deterrnine the masking byte to verify the OBFB line.
e) Write main program and a read and write subroutines to accept characters from keyboard
and to send them to print.
5) An 8255A PPI card is connected to 8085 microprocessor which has systern as shown in
figure below in which contol word is stored in address of F3H.
a) What are the addresses captured by 8255A PPI card?
b) Draw the minimum interfacing circuit.
c) Write down the control word to initialize the 8255A PPI card.
d) Write down the status word format for 8255A PPI card for the system.
e) Write down BSR control word to initialize port A interrupt request.
6) Interface a parallel bus centronics printer with 8085 microprocessor using 8255A in mode 1
output configuration.
a) Draw the necessary interfacing circuit required for this purpose using 8255 PPI in
handshake mode.
b) Determine port address as per your chip select logic.
c) Determine the control word required for printing operation.
d) Draw the timing waveform for transferring data to the printer.
e) Write an ALP to print characters whose ASCII code is available in memory location from
9000H.
7) A/D converter requires signal to start the conversion and indicates with the end of conversion
signal. 8255A PPI is interfaced with 8085 microprocessors at 80H. Microprocessor reads 8-
bits O/P data of the ADC at port A and display the same data to eight LED's connected at
port B of 8255A. State any assumptions made.
a) Identify the address captured by the card
b) Determine the necessary control words
c) Draw the schematic interfacing circuit
d) Write a program to perform the operation
8) Explain the different schemes of parallel data transfer with suitable timing diagram. Explain
the functional block diagram of 8255A PPI with neat diagram.
9) A microprocessor kit has an onboard 8255. Interface to the 8255 eight single-pole-double-
throw (SPDT) switches numbered S0 to S7 and a seven segment common anode LED display.
Draw the complete circuit setup. Define clearly the functions of all ports, write a program
to initialize 8255, detect a switch closure, and display the value of the switch number on the
LED display.
10) Assume that your group has decided to make microprocessor based instrumentation system
for an ice cream factory using an 8255 PPI card at base address 5000H in memory mapped
I/O mode for controlling purpose. You need to measure pressure and ternperature of a
manufacturing plant.
a) List out the collected documents and components.
b) List out different signals you need to derive and or can be directly connected to your
interfacing circuit.
c) Draw minimum mapping circuit for above system
d) What are the addresses captured by your card? Generate the control word for the system.
e) Write a progam module for measuring temperature and control if the temperature is not
in the range. Assume suitable data if necessary.
11) List out the technical benefits of using 8255 PPI in a MBI system.
12) With a neat timing diagram and an appropriate example, explain the operation of 8255 PPI
in mode 2. You should clearly show the necessary control signals and an interfacing circuit
to connect 8255 PPI to 8085 microprocessor. Also write the necessary control words to
configure the 8255 in this fashion.
13) Consider a double handshake scheme that allows data transfer from an input peripheral
device to an 8085 microprocessor through an 8255 PPI.
a) List all control signals that get exchanged between the devices.
b) Draw a detailed timing diagram showing the exchange of control and data signals.
Include the cause and effect arrows in your timing diagram.
c) With a neat sketch how the overall system diagram between the modules mentioned
above.
d) Generate an appropriate control word based upon your drawing and derive the address of
the control register of the 8255 PPI used in your design.
14) Assume that your group has decided to make PC based instrumentation control system for
automatic concrete purifying factory using an 8255 PPI card at base address 4000H in
memory mapped I/O mode for controlling purpose.
a) List out the collected documents and components.
b) List out the different signals you need to derive and or can be directly connected to your
interfacing circuit.
c) Draw minimum mapping circuit for the above system
d) What are the addresses captured by your card? Generate the control word for the system.
e) Write a progam module to read ten set of raw data from port A and port B; add the data
and store the result starting from address 4040H.
15) Write a short note on PCI Bus.
16) Write a short note on ISA Bus.
17) Interface a keyboard and a printer in mode 1. Port A is designed as input for keyboard with
interrupt I/O , port B is designed as output for printer with status check I/O. Draw the
mapping circuit and write the control word and address map.
18) In a microprocessor based system, an 8255A PPI card is used to interface a keyboard and a
printer to the processor. The 8255A PPI is interfaced with the 8085 microprocessor in the
system such that the base address of 8255 A PPI is 4044H.
a) What are the addresses captured by the card?
b) Draw the complete interfacing circuit of 8255A PPI with 8085 microprocessor for the
given system.
c) If the printer is interfaced to port A and the keyboard is interfaced to port B of the PPI
generate the control word to initialize the 8255A PPI with proper explanations. Both
printer and keyboard use 8-bit parallel data tansfer with handshaking
d) Derive the control word to enable interrupt request to the microprooessor by port A of
8255A PPI in above system with proper explanations.
19) An 8255A PPI connected to 8085 has a system base address of 80H.
a) What are the addresses assigned for Port A, Port B, Port C and control register?
b) Write down the control word to initialize this card as follows: Port A mode 0 output, Port
B handshake input, Port Cupper, output and remaining pin of Port Clower input.
c) For above case, write down bit set/reset control word to initialize Port B interrupt request.
***END OF REVIEW QUESTIONS***
Important Dates :
Assignment Issued: 2081 Jestha 22
Submission Deadline: 2081 Ashad 1, Saturday.
If you have any questions or need clarification, please contact :
: suwarna_mise004@ioepc.edu.np : 9800994284
